The reduction in the price of museum tickets for members is a clear example of a material incentive, which offers tangible financial benefits. This type of incentive encourages individuals to join the organization for economic reasons. Therefore, the correct answer is D. material incentive.
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A reduction in price for museum tickets due to membership is classified as a material incentive, which provides tangible financial benefits to members. Material incentives are aimed at appealing to individuals' economic interests, offering discounts or advantages. This contrasts with purposive or solidary incentives, which focus on values or social interactions. ;